Existing approaches to traffic speed estimation endeavor to develop speed estimates across traffic networks representing large geographic areas. Each such network is comprised of inter-connected links. There are existing systems that attempt to utilize GPS data to develop such speed estimates, but obtaining complete link speed estimates is hindered by the sparseness of the input data—i.e., GPS data is typically available for only part of the links representing a larger transportation network, and only for part of the time. In other words, collected GPS data is incomplete, making it hard for these existing systems to accurately estimate traffic speed across inter-connected network segments.
An example of such a system is found in U.S. Pat. No. 7,557,730, which discloses systems and methods for automatically collecting, correcting, merging, and publishing information about traffic, transit, weather, public events and other information useful to travelers. This system collects data on a continuous basis at one or more locations and uses GPS receivers of users of a network of traffic segments to do so. One problem with such a collection methodology is that GPS data does not record direction of travel, and there is interference between segments on unrelated routes that are close in latitude and longitude. For at least these reasons traveler information across multiple segments cannot be accurately determined. This prior art solution attempts to match links so that it knows what direction the vehicle is traveling, thereby solving for information that is not provided in GPS data.
Such a prior art system does not address the problem of filling in missing speed information that is normally part of the GPS data set for all links at all times in a transportation network. This prior art solution is therefore focused on a framework for figuring out direction of travel, rather than compensating for the sparseness of speed information due to an incomplete set of GPS data. There is therefore a need in the art for a system and method of using collected GPS data to estimate vehicle speed across an entire network of road segments in real-time where the collected GPS data does not provide complete speed information.